Conventionally, there is widely known a circuit pattern forming method that performs copper foil masking followed by etching. This method is, however, complicated in production process and time consuming, and needs expensive production equipment. In recent years, a technical field referred to as printed electronics is studied actively, where a circuit pattern is formed by printing, so as to simplify the production process and to reduce cost of the production equipment.
By way of example, in the Patent Document 1, there is disclosed a technique where a non-conductive film containing copper nanoparticles is deposited by using a printer such as an ink jet printer, and thus formed film is exposed to light from above, thereby fusing the copper particles, and then a conductive circuit is formed.